Hydroxyapatite is known as a bone substitute material.
In particular, nanoscale hydroxylapatite, i.e. hydroxylapatite having a mean particle size of less than 100 nm, is known and is being used as a paste for treating bone defects. In particular, hydroxylapatite is used which has a length of less than 200 nm as measured in a longitudinal direction of the particles. The particles are needle- or rod-shaped and have a small thickness of preferably less than 50 nm.
Also known are compressed or sintered form bodies made of hydroxylapatite which may be used as an implant.
Known hydroxylapatite pastes have the drawback of exhibiting a relatively low form stability which means that in many instances the paste is only suitable to a limited extent since it might be re-pressed out of the defect site after having been introduced, due to mechanical stresses. Moreover, handling of such pastes is often difficult.
Sintered bodies of hydroxylapatite, on the other hand, lack flexibility and are generally replaced only slowly by natural bone material.